The MAX232 device is a dual driver/receiver that converts between TTL/CMOS and RS-232 signal levels. It contains a charge pump that generates the voltages required by RS-232 from a single 5V supply. Each receiver converts ±30V RS-232 signals to 5V TTL/CMOS levels, and each driver converts TTL/CMOS signals to RS-232 levels. It is commonly used to interface between RS-232 ports and devices that use lower voltage digital levels like microcontrollers.